Document nkrjoDVdapzDx4MGLv9431NQ6

OSSSSSBOB^ ****** NATURE VOL 231 JUNE 18 1971 < Soktl, R.. *nd Sneaih, P. H. A., Principles of Numerical Taxonomy, 72 and 226 (Freeman, Sen Francisco and London. 1963). * Anderson, N. 0.. A'arwrc, 217, 1346 (197Q>. > snrtCtf. R. C. Trans. Roy. Soc. South Austral., 71, 212 (1947). 4 Glacuner. M. F,, end Wade, M., Palaeontology, 9, 399 (1966). * Glacstitrr, M. F., Bull, Geo!. Soc. Amer., Sates and Discussions (in the preit, 1971). * GUetwer, M, F., Biol. Ret., 37.467 (1962). > sjmJuis, K., Biol. Ret., 39,487 (1964). 467 The age? and body weight of control and PCH-loaded birds were compared, and no significant differences were found. Both groups had gained weight equally by comparison with bird* weighed immediately after trapping at Falsterbo10. Table 1 Oro*noehlorin* Residua* (ng/g Fresn Weight) in 8ree*t Muscles of Robins Effect of PCB on Nocturnal Activity in Caged Robins, Erithacus rubecula L. Chlorinatsd hydrocarbons are a recognized threat to populalions of wild birds, but (heir precise mode of ecological action is largely unknown. They are, however, known to have a thinning effect on the egg shell1 J, and they react with some hormones**4, thus affecting the endocrine balance of the body. Such findings suggest that these substances may exert a profound influence on the activity and behaviour of contaminated animals, but little attention has been devoted to this aspect. The migratory activity of birds is governed chiefly by the interplay of hormonal systems' *, and the orientation of the migrants Is a highly refined instinct pattern. This suggests that the nocturnal activity of affected migratory birds might he a suitable indicator of the possible ecological effects of organochlorines. Tlte robin, Erithacus rubecula L., in Sweden is almost com pletely migratory, moving exclusively by night Its main flight direction during the autumn migration is SW-SSW. Robins were trapped at Falsterbo Bird Station (53* 23' N, 12* SO' E) in the last week of September 1970. They were kept singly in opaque plastic containers under a natural light-dark rhythm and were fed mealworms and berries ad lib. Beginning on October 2, twenty-eight robins were given one extra meal worm each day, injected with S ug of `Clophen A50', a poly chlorinated biphenyl (PCB). These worms were marked with a small dot of red dye to enable us to determine whether the worm had been eaten; in a few cases it was not taken. Eighteen robins were kept in identical conditions but were not given worms containing PCB. The experiments were performed between 1900 and 2100 on October 21 and 22 (within the normal migratory period of Swedish robins) on birds which had eaten eleven to thirteen PCB-ioaded worms. The experimentally contaminated and control birds were placed singly in EmJen funnels under the open sky at a site 20 km east of Lund, where no artificial light sources interfered. During the first night the sky was overcast, and the experiment was discontinued after 35 min because of rain. During the second night, cloud-cover was approxi mately 1/8, and the experiment was continued for 73 min as planned. The evaluation of the activity sums and of the mean vectors of the birds followed the procedures described by Rabor'*. On the first occasion, twenty PCB-ioaded and twelve control birds were tested, and on the second, nineteen and eleven birds, respectively. With a few exceptions, the same individuals were used in both experiments. The average activity sums were compared separately for each night using a Mann-Whitney U test (two-tailed). The average activity on the first night was much higher in the PCB-ioaded birds than in the controls, but the difference was not quite significant. On the second night, when the experi ment ran for a longer period, the average activity of the PCB-loaried birds was significantly higher than that of the controls (P<0.0$). The dispersion of the megn vectors was treater on the overcast night of October 2! than on the follow ing night which was cloudless. No significant differences between PCB-ioaded and control birds with respect to direction or dispersion were detected on either night. The direction was the same at the supposed standard migratory direction of Swedish robins. Birds fed with PCB Control birds of PCB ingested 60 33 63 33 60 53 -- p.p'-DDE 93 96 75 64 91 56 72 69 70 66 p.p'-DDT 7 2J 23 24 22 2 23 27 30 25 PCB 373 467 34i 164 365 287 120 70 90 31 The breast muscles of six PCB-ioaded birds and four control birds were analysed by gas chromatography for organochlorine content (Table I). The apparatus consisted of a Varian Aerograph 204 gas chromatograph equipped with electron capture detectors, and three different columns using SF 96 (4 %), QP I (8 %) and SF 96/QFI (3:1) as the stationary phases on GasChrom P (100/120 cneth) were utilized. The iden tity of the more important compounds detected was also con firmed by chemical techniques. The PCB level in the experi mentally contaminated birds was four times that found in the controls, the difference being statistically highly significant, but it was in unexpectedly low concentration, indicating that much of it had been excreted or stored elsewhere than in the breast muscles. Both groups of birds were also analysed for p.pDDE and p.p'-DDT, but no significant differences were 'detected. These results demonstrate an effect of organocbJorine residues on the activity patterns of the bird. Gwinner11 demonstrated a correlation between the degree of migratory activity (restlessness)' and the distance between the breeding and wintering quarters in different warbler species of the gcr.u> Pkylloscopus. A quantitative change in such activity Therefore assumes great ecological significance. The rapid mobilization of fat during migration is also an important aspect of this proWem'1'1*. PCB compounds occur widely in the global ecosystem and. like other chlorinated hydrocarbons, they accumulate in rood chains14'1'. Their effects, even at the relatively low levels used in these experiments, indicate that they arc important environmental contaminants. S. Ulfstrasd A. SbDCRGRCN Department of Animal Ecology, Ecology Building. University of Lund, 5-223 62 Lund Zoological Laboratory, University of Copenhagen, Universitetsparken 15, DK~2100 Copenhagen Received March 29, 1971. HUNS O0171? 468 RalcUlfr, D. A.. J. Appl. tcol., 7, 67 (1970). * Peakali, D. 8., Science, 168. 592 (1970). * Peakali, D. B., Nature, 216, 505 (1967). * linear, J. L.. and Peakali, 0. B,, Nature, 228, 783 (1970). * Furrier, D. S., Proc. Xt V Intern. Orn. Cong. Oxford, 1966, 107 (Blackwell, Oxford and Edinburgh, 1967). * BerthoUl, IV. Zaai. Jb. Syst., 96, 491 (1969). 7 Rabid, )., Orn. Scant!., 1, 27 (1970). * RubtU J., Dttnsk Orn. For. Tidsskr., 64, 118 (1970). * Svcnsxon, l.. Identification Guide to European Passerines (Nal- urhist. Kiksmus., Slockliolm, 1970). Scott, II. F... Vdr FJfeiv , 24. 156 (1965). " Gwinner, E., J.f. Orn., 109, 70(1968). 11 Helms, C. W., Miner. Zoo!., 8, 151 (1968). '* Hussell, D. J. T., Auk, 86, 75 (1969). " Kincbrough, R. W.. Rieche, P., Peakali, D. It., Herman, S. G., and Kirven. M N., Nature. 220. 1098 (1968). '* Jensen, S., Jolmels, A. G , Olsson, M., and Otterlind, G., Nature, 124, 247 (1969). Skua Numbers and Conservation Problems at Cape Hallett, Antarctica Thi flora and fauna of Antarctica are often considered to be secure, principally because of international treaty obligations. Nevertheless, several people have already drawn attention to conservation problems' which are underlined by my own work on the decline of the South Polar skua (Catharacta maccormickt) at Cape Hallett (lat. 72* 18'S, long. 170* 19' E). During the two austral summers of 1967-68 and 1968-69, l made an intensive study of the decline of the skua and of skuapenguin feeding relationships, which will be published in full later. Data gathered by Dr T. S. Choate in the 1966-67 season are also incorporated in this report. Decause of the scarcity of suitable coastal building sites, man sometimes competes directly with nesting birds for space. In December 1956, for example, when the joint United StatesNcw Zealand station was established, 3,318 juvenile and at least 4,900 adult Adelie penguins (Pygoscelis adetiae) were removed from the Hallett rookery4, and at that time the breeding popu* lution was probably between 56,000 and 62,000 pairs*. Although indications of the size of the resident skua breeding population are available4*4, the first census was of 181 pairs in the 1960-61 season1. Census records in subsequent seasons reveal a drastic decline in the numbers of skua pairs breeding; these are 162 pairs in 1963-64 and 147 pairs in I96S-66 (per sonal communication from F. C. Kinsky); 113 pairs in 1966-67 (pcrsonul communication from T. S. Choate); 105 pairs in 1967-68 and 98 pairs in 1968-69 (my own work). Thus there has been u 54% decline diirin> nine seasons. Census records of the Adelie penguin breeding population made by Choate (1967-68) and Westerskov (1968-69) indicate a decrease of a similar magnitude during the same period (personal communi cation from Choate and K. E. Westerskov). The decrease in the number of skuas during and between the three seusons studied was determined from the recovery records of bunded birds. During (his period 95-98% of the breeding population and many non-breeding biids were marked with numbered monel-metal bnnds. There was no significant loss of these bauds. The mean annual loss of breeding skuas was 18% compared with 6% for a stable population of skuas at Cape Go/ier (personal communication from R. C. Wood). This result for the Hallett skuas probably represents a perma nent loss of birds rather than sporadic return or breeding. Of the fifty breeding birds lost between 1966-67 and 1967-68, for example, only ono was recovered in the 1968-69 season and us a non-breeder. During the three seasons, twenty-three skuas, including eight breeding birds, were found dead or dying. The cause of death was established in only six cases, all resulting from human activities (wing breakages or rupiured crops caused by the NATURE VOL 23t JUNE 18 ingestion of corn cobs). No breeding birds disappeared \ out trace. Seasonal losses are therefore only slightly gr< than might be expected for a stable population. Nigh seas mortalities, however, have been recorded. In 1965-66 Ki recorded the deaths of thirty-three adult skuas. He anal three of these, and discovered that they had been poisonc ingesting parts of lead battery plates. Figures for fledgling production (chicks flcdged/fen breeding) during the period of the decline are heterogcnc 59/156 in 1959-60 (ref. 6), 116/181 in 1960-61 (ref. 7), 36 in 1966-67 (personal communication from Choate), 4|/|( 1967-68 and 24/98 in 1968-69 (x2-21.2, /<0 001). It. I ever, the 1960-61 data are removed from the calculation significant deviation remains (x1 = 3.57, P>0.25) and resulting mean annual figure of 0.34 fledglings per hrec female compares favourably with the value of 0.33 for Hedi production at the stable Cape Cro/ier colony (personal i munication from Wood). The high tledgling prodvu in 1960-61 was probably, therefore, unusual, and (his t meter does not seem to have changed significantly dunm period of the decline. The effect of any alteration in lied? production on the decline could, however, be recorded after 5-6 yr, the approximate age of first breeding. I conclude that the decline of the skua population has he result of adults abandoning the Hallett colony as a brearea. This decline has coincided with a period of human u pation and with the decline of the Adelie penguin popuia on which skuas prey and scuvenge for food. The dechr penguins has itself been established as resulting directly l human disturbance (personal communication from Choate Westerskov). Thus although the skua decline hus bcci ultimate consequence of human activity, the relative import of direct disturbance as distinct from the penguin decline proximate cause requires evaluation. This aspect of the s which has provided new information about the relation between skuas and penguins will be published later. In spile of suggestions by several workers for the climina of possible sources of poisoning and the reduction of di-a ance to both penguins and skuas, this ignominious situatioi continued virtually for h decade. Holdgute* points out I although the agreed measures for conservation under Antarctic Treuty are comprehensive and therefore should require significant future amendment, three areas for impr ment remain, especially with regard to specialty prote localities or species. These areus are the perfection of application of the agreed measures, the development of po> schemes for management and the adoption of cducati means to ensure that all personnel visiting Antarctica are a' of the need for conservation. This report should serv endorse Holdgate's suggestions for the improvement of cm vation in the Antarctic, particularly as Cape Hallett is class as a specially protected area. I thank DrT. S. Choate, Mr F. C. Kinsky. Mr R. C. and Dr K. E. Westerskov for valuable information. Brian R. Johnsk Zoology Department, University of Otago, Dunedin, New Zealand MQNS Qti 1 7 lti Received March II; revised April 15. 1971. 1 Storehouse. B., N7. Set. Per., 23. .1 (196>). 7 Shimoir.umi.Antarctic !\idu-sc (edit I'y HuM-*:iiif. M W i ' (Academic Press. London. 1970). 4 Holdnine. M. W . Antarctic t'.coUniy (edit, liy HoUkalc, M 2, 924 (Academic Pres*. London. 1970) 4 I'klund, C. U,, Pail-Dandlin', 32. 283 (19611 5 Reid. 1). E.. Ntitminx. 15. I'M (1068). 4 Reid. It. K.. NX DSIR Anton lie Hit liep (Wfth. 1 Maher. W. J.. Not. Hist., 75. 42 (1966)